Glare
Glare from luminaires significantly impairs visual comfort.
At the same time, untidy edges where light beams meet the wall, with artifacts, or differing light colors have a disruptive effect in the space.
The light emphasizes only isolated spots on the ceiling. The areas where brightness is actually needed are not addressed.
Material
Diffused light
Diffused light creates hardly any shadows and models surfaces only weakly. As a result, structure, depth, and brilliance are lacking. Materials with glossy surfaces often appear less high-quality under diffused light, since reflections and contrasts are not brought out sufficiently.
Directional light
Directional light uses shadow to create stronger modeling and gives the space more depth. It creates brilliance and makes glossy materials appear more sophisticated. With reflective surfaces, however, the possibility of reflected glare needs to be taken into account.
An angle of incidence of 30° is considered ideal for avoiding distracting reflections, for example on pictures or glossy surfaces.
Intense cast shadows model fine textures particularly clearly and reveal surface structures. With glossy materials, however, potential reflected glare needs to be taken into account.